They aren’t. From a comment on https://www.reddit.com/r/ublock/comments/32mos6/ublock_vs_ublock_origin/ by u/tehdang:

For people who have stumbled into this thread while googling "ublock vs origin". Take a look at this link:

http://tuxdiary.com/2015/06/14/ublock-origin/

"Chris AlJoudi [current owner of uBlock] is under fire on Reddit due to several actions in recent past:

• In a Wikipedia edit for uBlock, Chris removed all credits to Raymond [Hill, original author and owner of uBlock Origin] and added his name without any mention of the original author’s contribution.
• Chris pledged a donation with overblown details on expenses like $25 per week for web hosting.
• The activities of Chris since he took over the project are more business and advertisement oriented than development driven."

So I would recommend that you go with uBlock Origin and not uBlock. I hope this helps!

Edit: Also got this bit of information from here:

https://www.reddit.com/r/chrome/comments/32ory7/ublock_is_back_under_a_new_name/

TL;DR:

• gorhill [Raymond Hill] got tired of dozens of "my facebook isnt working plz help" issues.
• he handed the repository to chrismatic [Chris Aljioudi] while maintaining control of the extension in the Chrome webstore (by forking chrismatic's version back to himself).
• chrismatic promptly added donate buttons and a "made with love by Chris" note.
• gorhill took exception to this and asked chrismatic to change the name so people didn't confuse uBlock (the original, now called uBlock Origin) and uBlock (chrismatic's version).
• Google took down gorhill's extension. Apparently this was because of the naming issue (since technically chrismatic has control of the repo).
• gorhill renamed and rebranded his version of ublock to uBlock Origin.